How to Roll Your Own Pipe
Kevin needs some 4" diameter pipe for a new "ball and post" sculpture, so rather than buy standard 3/8"-wall pipe from his local steelyard, he makes his own pipe that's light enough to create the illusion he is seeking. He starts by cutting 16 gauge steel sheets into 4' x 8' sections using his foot shear (also called a jump shear). Then he grinds off the scale the edges so he can easily weld it after bending. Kevin then moves to his 52" Dayton slip roll, which lets him bend up to 16 gauge metal. It has three rollers, two in the front that he can adjust up and down to pinch the metal to feed it through. The back roller has two adjustments that let him move each side of the roller independently. It can go up and down and also tilt, which is handy if he wants to curve one side of the metal more than the other. He adjusts the back roller by twisting the adjustment knobs on each side the same number of times. The big electrical machines might be able to bend these steel sheets into a cylinder in a single pass, but his slip roll is a manual machine. So he has to make seven to 10 passes to roll each sheet of steel into a cylinder. His slip roll is rated to 16 gauge, the same gauge of steel he is using, so it is right at the limit of the machine. Because the steel sheets are so wide in relation to the size of the slip roll, it takes several passes to get the full cylinder. Kevin says he has the machine set up a little high as it is, so he bends the steel a little between the rollers to get it started. Then he flips it around and runs it through again from the opposite side to make it is as rounded as possible, getting rid of the flat area that develops between the front and back rollers for a smoother curl. He'll bend all of his sheets at once so he can just adjust the back roller once for each pass. It gets harder to turn roll the metal as the cylinder gets tighter. As it gets tighter, he goes from 10 turns each of the adjustment knobs to half that many so he can keep a closer eye on the shape. When he gets close to the last pass, he measures the distance between the slip roll stand and the bottom of the back roller to make sure it is the same. He explains that he'll tack weld the newly formed cylinder on each end, then TIG weld the length of the seam. He'll grind the weld smooth, then roll what is now a pipe through the slip roll again to smooth its form and hide the weld. Finally, he shows how he gets the nearly-closed cylinder, or tube, off the slip roll by opening the feed rollers and sliding it off.
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